Waterborne coating composition

ABSTRACT

A waterborne coating composition containing an aqueous dispersion of a polymer, the polymer being substantially free from hydroxyl, primary amino, and secondary amino groups and the polymer bearing at least two active methylene groups, and an aqueous dispersion of a polyisocyanate bearing at least two isocyanate groups is provided. Also provided is a method of improving the chemical resistance of a coating and a substrate coated with the waterborne coating composition.

This is a divisional of application Ser. No. 08/224,923, filed Apr. 8,1994 U.S. Pat. No. 5,414,041.

FIELD OF THE INVENTION

This invention relates to a waterborne coating composition containing anaqueous dispersion of a polymer, the polymer being substantially freefrom hydroxyl, primary amino, and secondary amino groups and the polymerbearing at least two active methylene groups; and an aqueous dispersionof a polyisocyanate bearing at least two isocyanate groups.

BACKGROUND OF THE INVENTION

Waterborne polymeric compositions such as clear or pigmented coatingsare frequently required to supplant solvent-containing compositions dueto effective and pending concern and legislation regarding the emissionof volatile organic compounds into the atmosphere. Solvent-bornepolyurethane coatings formed from the reaction of a multi-functionalisocyanate with multi-functional oligomers and polymers bearing activehydrogen functionality such as, for example, acrylic polyols, are widelyused for their excellent performance properties. Polyurethaneperformance properties including excellent chemical resistance can beattained under ambient curing conditions, although isocyanate-containingcompositions most frequently must be used as two-pack compositions,i.e., mixed shortly before use, due to the inherent reactivity of theisocyanate and active hydrogen groups. The high performance ofpolyurethanes in an aqueous composition is highly desirable. Suchurethane compositions formed from an aqueous polyisocyanate and anaqueous polyol dispersion, for example, are known; however, residualhydroxy or amino groups remaining after the reaction with thepolyisocyanate may detract from the stain and chemical resistance of thecured composition. Compositions containing aqueous dispersions ofpolyisocyanates which provide superior properties are needed by thecoatings industry.

DESCRIPTION OF THE PRIOR ART

U.S. Pat. No. 5,075,370 discloses an aqueous two-component coatingcomposition which contains an aqueous solution and/or dispersion of apolymer containing hydroxyl groups and an emulsified polyisocyanatecomponent.

U.S. Pat. No. 5,200,489 discloses a composition which contains awater-dispersible polyisocyanate composition having an average NCOfunctionality of 2 to 6 and an aqueous resin containingisocyanate-reactive groups.

None of the references discloses a waterborne coating compositioncontaining an aqueous dispersion of a polymer, the polymer beingsubstantially free from hydroxyl, primary amino, and secondary aminogroups and the polymer bearing at least two active methylene groups; andan aqueous dispersion of a polyisocyanate bearing at least twoisocyanate groups.

STATEMENTS OF INVENTION

According to a first aspect of the present invention there is provided awaterborne coating composition containing an aqueous dispersion of apolymer, the polymer being substantially free from hydroxyl, primaryamino, and secondary amino groups and the polymer bearing at least twoactive methylene groups; and an aqueous dispersion of a polyisocyanatebearing at least two isocyanate groups.

According to a second aspect of the present invention there is provideda method of improving the chemical resistance of a coating by forming awaterborne coating composition by admixing an aqueous dispersion of apolymer, the polymer being substantially free from hydroxyl, primaryamino, and secondary amino groups and the polymer bearing at least twoactive methylene groups; and an aqueous dispersion of a polyisocyanatebearing at least two isocyanate groups; applying the coating compositionto a substrate; and curing the coating composition.

According to a third aspect of the present invention there is provided asubstrate bearing a cured waterborne coating composition containing anaqueous dispersion of a polymer, the polymer being substantially freefrom hydroxyl, primary amino, and secondary amino groups and the polymerbearing at least two active methylene groups; and an aqueous dispersionof a polyisocyanate bearing at least two isocyanate groups

DETAILED DESCRIPTION OF THE INVENTION

This invention is directed to a waterborne coating compositioncontaining an aqueous dispersion of a polymer, the polymer beingsubstantially free from hydroxyl, primary amino, and secondary aminogroups and the polymer bearing at least two active methylene groups; andan aqueous dispersion of a polyisocyanate bearing at least twoisocyanate groups. A "waterborne coating composition" herein is definedas a composition in a medium which is predominantly composed of water.The medium may be water or a mixture of water and at least onewater-miscible solvent such as, for example, ethylene glycol butyl etherand propylene glycol propyl ether which does not react with isocyanategroups to a substantial degree during the pot-life of the coating. Thepot-life of the coating is the period of time after forming the coatingcomposition during which the coating remains useable, that is, duringwhich no substantial viscosity increase occurs and during which nosubstantial attrition in the coating properties of the applied curedcoating results.

The aqueous dispersion of a polymer substantially free from hydroxyl,primary amino, and secondary amino groups bearing at least two activemethylene groups in the waterborne polymeric composition may be preparedby the addition polymerization of at least one ethylenically unsaturatedmonomer such as, for example, acrylic ester monomers including methylacrylate, ethyl acrylate, butyl acrytate, 2-ethylhexyl acrylate, decylacrylate, methyl methacrylate, butyl methacrylate, and laurylmethacrylate; acrylamide or substituted acrylamides; styrerie orsubstituted styreries; butadiene; vinyl acetate or other vinyl esters;vinyl monomers such as vinyl chloride, vinylidene chloride, N-vinylpyrrolidone; acrylonitrile or methacrylonitrile. By "active methylenegroups" herein is meant the esters and amides of acetoacetic acid,malonic acid, and cyanoacetic acid. Preferred are the esters ofacetoacetic acid. When monomer(s) which do not bear active methylenegroups are used exclusively in the formation of the polymer or whenadditional acetoacetate groups are desired, acetoacetate groups may beintroduced by the use of acetoacetate-functional chain transfer agentsas disclosed in U.S. Pat. No.4,960,924, hereby incorporated herein byreference, or by post-reaction of a copolymerized monomer. Cyanoacetatesand cyanoacetamides may be prepared by methods known in the art asdisclosed, for example, in U.S. Pat. Nos. 3,554,987: 3,658,878; and5,021,511, hereby incorporated herein by reference. In general, anypolymerizable hydroxy- or amino- functional monomer can be converted tothe corresponding acetoacetate or acetoacetamide, before or afterpolymerization, by reaction with diketene or other suitableacetoacetylating agent (See e.g. Comparison of Methods for thePreparation of Acetoacetylated Coating Resins, Witzeman, J. S.; DellNottingham, W.; Det Rector, F. J. Coatings Technology; Vol. 62, 1990,101 (and references contained therein)). Preferred is thecopolymerization of from about 5% to about 25%, by weight, based on thetotal monomer weight, ethylenically unsaturated monomer bearingacetoacetate functionality such as, for example, vinyl acetoacetate,acetoacetoxyethyl acrylate, acetoacetoxyethyl methacrylate (AAEM),acetoacetoxypropyl methacrylate (AAPM), allyl acetoacetate,acetoacetoxybutyl methacrylate, 2,3-di(acetoacetoxy) propylmethacrylate. Especially preferred is the aqueous dispersion of apolymer bearing at least two acetoacetate groups containing from about10% to about 20%, by weight, based on the total monomer weight,acetoacetoxyethyl methacrylate.

Low levels of ionic monomers such as, for example, from about 0.1% toabout 5%, by weight, based on the total monomer weight, (meth)acrylicacid, itaconic acid, crotonic acid, fumaric acid, maleic acid,monomethyl itaconate, monomethyl fumarate, monobutyl fumarate, maleicanhydride, dimethylaminoethyl (meth)acrylate,2-acrylamido-2-methyl-1-propanesulfonic acid, sodium vinyl sulfonate,and phosphoethyl methacrylate may also be incorporated in the polymerbearing at least two active methylene groups. Low levels ofmulti-ethylenically unsaturated monomers such as, for example, fromabout 0.01% to about 10%, by weight, based on the total monomer weight,ethyleneglycol dimethacrylate, divinyl benzene, allyl methacrylate,1,4-butylene glycol dimethacrylate, 1,6-hexanediol diacrylate, anddiailylphthalate, may also be incorporated in the polymer.

"Substantially free from hydroxyl, primary amino, and secondary aminogroups" as used herein means that monomers bearing such groups are notincorporated into the polymer; but low levels of adventitious hydroxyl,primary amino, or secondary amino groups may be present as impurities inthe monomer or initiator used or may be formed during the polymerizationor storage of the polymer. In any event, less than about 0.2%, by weightbased on polymer weight, of hydroxyl, primary amino, and/or secondaryamino groups are present in the polymer.

The glass transition temperature(Tg) of the polymer substantially freefrom hydroxyl, primary amino, and secondary amino groups and bearing atleast two active methylene groups is preferred to be from about -30° C.to about +45° C., as measured by differential scanning calorimetry(DSC). The emulsion polymer samples were dried, preheated to 120° C.,rapidly cooled to -100° C., and then heated to 150° C. at a rate of 20°C./minute while data was being collected. The Tg was measured at themidpoint using the half-height method. More preferred is a Tg from about-10° C. to about +45° C.

The emulsion polymerization techniques preferred to prepare the aqueousdispersion of a polymer substantially free from hydroxyl, primary amino,and secondary amino groups and bearing at least two active methylenegroups are well-known in the art. Conventional surfactants may be usedsuch as, for example, anionic and/or nonionic emulsifiers such as alkalior ammonium alkyl sulfates, alkyl sulfonic acids, fatty acids, andoxyethylated alkyl phenols. The amount of surfactant used is usually0.1% to 6% by weight, based on the weight of total monomer. Eitherthermal or redox initiation processes may be used. Conventional freeradical initiators may be used such as, for example, hydrogen peroxide,t-butyl hydroperoxide, ammonium and/or alkali persulfates, typically ata level of 0.05% to 3.0% by weight, based on the weight of totalmonomer. Redox systems using the same initiators coupled with a suitablereductant such as, for example, isoascorbic acid and sodium bisulfitemay be used at similar levels. Chain transfer agents such as, forexample, mercaptans may be used during the polymerization reaction inorder to moderate the molecular weight of the polymer.

The particle size of the emulsion-polymerized polymer substantially freefrom hydroxyl, primary amino, and secondary amino groups and bearing atleast two acetoacetate groups is from about 50 nanometers to about 500nanometers in diameter. The solids content of the aqueous dispersion ofa polymer bearing at least two active methylene groups may be from about20% to about 70% by weight.

The particles of the emulsion-polymerized polymer substantially freefrom hydroxyl, primary amino, and secondary amino groups and bearing atleast two active methylene groups may contain two or more polymericphases such as, for example, an inner phase and an outer phase, whereinthe outer phase is the predominant phase in contact with the aqueousmedium in which the particle is dispersed. Such particles are commonlymade by multi-stage emulsion polymerization wherein the individualstages differ in composition. Some particles which contain two or morepolymeric phases are core/shell particles, core/shell particles withshell phases incompletely encapsulating the core, core/shell particleswith a multiplicity of cores, interpenetrating network particles, andthe like. When multi-stage emulsion polymers bearing at least twoacetoacetate groups are used, the Tg of the outer phase or shell polymeris preferred to be from about -10° C. to about +45° C.; the Tg of theinner phase or core polymer is preferred to be from about 25° C. toabout 120° C.; the Tg of the inner phase or core polymer is morepreferred to be from about 45° C. to about 90° C.; the ratio of theweight of the inner phase or core polymer to the weight of the outerphase or shell polymer is preferred to be from about 20/80 to about80/20; the weight average molecular weight, as measured by gelpermeation chromatography, of the outer phase or shell polymer ispreferred to be from about 20,000 to about 10,000,000; and theacetoacetate groups are preferred to be in the outer phase or shellpolymer composition.

In one embodiment of this invention acetoacetate-functional polymericbinder is treated with about a stoichiometric amount of ammonia orprimary amine to form an enamine. Vinyl polymers containing pendantacetoacetate are prone to hydrolysis in water particularly on heataging. However, this problem may be eliminated by treating the aqueousacetoacetate polymer, after preparation and neutralization with onemolar equivalent of ammonia or a primary amine such as ethanolamine,methyl amine, isopropyl amine, butyl amine, or diglycol amine.

The waterborne coating composition contains, in addition to an aqueousdispersion of a polymer substantially free from hydroxyl, primary amino,and secondary amino groups and bearing at least two active methylenegroups; and an aqueous dispersion of a polyisocyanate bearing at leasttwo isocyanate groups. The polyisocyanate may contain aliphatically,cycloaliphatically, araliphaticaily and/or aromatically bound isocyanategroups. Suitable water-dispersible isocyanates and methods of makingaqueous dispersion of isocyanates therefrom are described in U.S. Pat.Nos. 4,663,337; 5,075,370; 5,185,200; 5,200,489; and 5,252,696; andEuropean Patent Applications EP 486,881 and EP 516,277; herebyincorporated herein by reference. Preferred is an aqueous dispersion ofa polyisocyanate bearing two to four reactive isocyanate groups.

The waterborne coating composition is formed from an aqueous dispersionof a polymer substantially free from hydroxyl, primary amino, andsecondary amino groups and bearing at least two active methylene groups;and an aqueous dispersion of a polyisocyanate bearing at least twoisocyanate groups by admixing the components using conventional methodssuch as mechanical agitation. The water-dispersible polyisocyanate maybe previously dispersed in a non-reactive or in an aqueous medium or itmay be dispersed in the presence of the aqueous polymer dispersion.

The ratio of equivalents of isocyanate groups to equivalents of activemethylene groups in the waterborne composition may range from about 0.1to about 5.0. Preferred is a ratio of equivalents of isocyanate groupsto equivalents of active methylene groups from about 0.5 to 2.0.

The waterborne coating composition may contain, in addition to theaqueous dispersion of a polymer bearing at least two active methylenegroups and an aqueous dispersion of a polyisocyanate, conventionalcomponents such as, for example, emulsifiers, pigments, fillers,coalescing agents, anti-migration aids, aqueous solutions or dispersionsof non-functional polymer (by "non-functional polymer" herein is meantpolymer free from primary amino, secondary amino, hydroxyl, isocyanate,or active methylene groups), curing agents, thickeners, humectants,wetting agents, biocides, plasticizers, antifoaming agents, colorants,waxes, and anti-oxidants. It is preferred that all such conventionalcomponents do not substantially react with active methylene orisocyanate groups within the potlife of the waterborne coatingcomposition.

The substrates to which the waterborne coating composition of thisinvention may be applied include wood, plastic, leather, paper, wovenand nonwoven fabrics, metal, plaster, cementitious and asphalticsubstrates, previously primed or coated substrates, and the like. Thecured waterborne coating composition may fulfill a decorative orprotective function, or both, or may act as a primer or as an adhesivewhen disposed between two coatings or between two such substates.Preferred substrates are wood, metal, and plastics. The coatingcomposition of this invention may be applied to a substrate by methodswell known in the art of applying coatings such as air-assisted spray,airless spray, plural component spray guns, brush, roller, squeege, rollcoater, curtain coater, and the like.

After the waterborne coating composition is applied to a substrate thecoating composition cures, that is, reaction between the activemethylene groups and the isocyanate groups is believed to occur. Curingto yield useful coatings properties may take place at a convenient rateat ambient temperatures such as, for example, about 0° C. to about 35°C.. However, it is sometimes desirable to accelerate the rate ofproperty development by heating the applied waterborne composition to atemperature from about 35° C. to about 200° C. Preferred is a curingtemperature from about 25° C. to about 120° C. for coatings applied toheat-stable substrates and from about 25° C. to about 50° C., forsubstrates sensitive to higher temperatures.

The following examples are intended to illustrate the waterborne coatingcomposition containing an aqueous dispersion of a polymer bearing atleast two active methylene groups and an aqueous dispersion of apolyisocyanate bearing at least two isocyanate groups. They are notintended to limit the invention as other applications of the inventionwill be obvious to those of ordinary skill in the art.

EXAMPLE 1 Preparation of aqueous dispersion of polymer

Preparation of Sample 1 and Comparative sample A. To a 5 liter stirredreactor 1383.0 g. deionized water (DI water) and 48.2 g. of an aqueoussolution of sodium dodecylbenzenesulfonate (23% active ingredient )which had been heated to 85° C. was added 43.4 g. of Monomer Emulsionwhich was then rinsed into the reator with 15 g. of DI water. A solutionof 2.08 g. of ammonium persulfate in 15.0 g. DI water and a solution of2.08 g. sodium carbonate in 45 g. DI water was then added. Ten minutesafter the first addition, the temperature was 85° C. and the uniformaddition of the remainder of ME and a solution of 2.08 g. ammoniumpersulfate in 150.0 g. DI water were begun. The temperature remainded at85° C. over the 180 minute period during which ME and catalyst wereadded. A catalyst/activator pair was added after the ME and catalystfeeds were complete. The final reaction mixture was neutralized to pHrange of 7.5 with 29% aqueous ammonia. Comparative Sample A had aBrookfield viscosity of 22 cps at a weight % solids contents ofapproximately 38.3% and a particle size of 81 nanometers. Sample 1 had aBrookfield viscosity of 9 cps at a weight % solids contents ofapproximately 37.7% and a particle size of 80 nanometers.

                  TABLE 1.1                                                       ______________________________________                                        Monomer Emulsion for Comparative Sample A.                                    ______________________________________                                        DI water              425.60                                                  Anionic Surfactant (23% active)                                                                     87.36                                                   Butvi Acrylate        806.48                                                  Methvi Methacrylate   551.51                                                  Methacrvlic acid      27.71                                                   ______________________________________                                    

                  TABLE 1.2                                                       ______________________________________                                        Monomer Emulsion for Sample 1.                                                ______________________________________                                        DI water              425.60                                                  Anionic Surfactant (23% active)                                                                     87.36                                                   Butyl Acrylate        708.08                                                  Methyl Methacrvlate   511.32                                                  Acetoacetoxy ethyl Methacrvlate                                                                     138.60                                                  Methacrylic acid      27.71                                                   ______________________________________                                    

EXAMPLE 2 Preparation of aqueous dispersion of polymer

Preparation of Samples 2-3 and Comparative Samples B-C. To a 5 literstirred reactor 1383.0 g. deionized water (DI water) and 48.2 g. of anaqueous solution of sodium dodecylbenzenesulfonate (23% activeingredient ) which had been heated to 85° C. was added 43.4 g. ofMonomer Emulsion #1 (ME#1) which was then rinsed into the reactor with15 g. of DI water. A solution of 2.08 g. of ammonium persulfate in 15.0g. DI water and a solution of 2.08 g. sodium carbonate in 45 g. DI waswas then added. Ten minutes after the first addition, the temperaturewas 85° C. and the addition of the remainder of ME #1 and a solution of1.04 g. ammonium persulfate in 75.0 g. DI water was begun. Thetemperature remained at 85° C. over the 90 minute period during which ME#1 and the cofeed catalyst # 1 was added. Thirty minutes later, thetemperature was 85° C. and the addition of Monomer Emulsion #2 (ME #2)and catalyst #2 was begun. The temperature was 85° C. during the 90minute period over which ME #2 and Catalyst #2 was added. Acatalyst/activator pair was added after the ME #2 feed was completed.The final reaction mixture was neutralized to a pH of 7.5 with 29%aqueous ammonia. Sample 2 had a Brookfield viscosity of 28 cps at aweight % solids content of 37.5% and a particle size of 71 nanometers.Comparative Sample B had a Brookfield viscosity of 113 cps at a weight %solids content of 37.8% and a particle size of 76 nanometers.Comparative Sample C had a Brookfield viscosity of 36 cps at a weight %solids content of 37.6% and a particle size of 70 nanometers. Sample 3had a Brookfield viscosity of 26 cps at a weight % solids content of38.1% and a particle size of 71 nanometers. Sample 4 had a Brookfieldviscosity of 21 cps at a weight % solids content of 37.9% and a particlesize of 76 nanometers.

                  TABLE 2.1                                                       ______________________________________                                        Monomer Emulsions for Sample 2                                                ______________________________________                                        ME #1                                                                         DI water              212.84                                                  Anionic Surfactant (23% active)                                                                     43.68                                                   Methyl Methacrylate   557.02                                                  Butyl Acrylate        73.43                                                   Styrene               55.42                                                   Methacrylic acid      6.93                                                    ME #2                                                                         DI water              212.84                                                  Anionic Surfactant (23% active)                                                                     43.68                                                   Butyl Acrylate        372.70                                                  Methyl Methacrylate   146.90                                                  Acetylacetoxy ethyl Methacrylate                                                                    138.60                                                  Methacrylic acid      34.60                                                   ______________________________________                                    

                  TABLE 2.2                                                       ______________________________________                                        Monomer Emulsions for Comparative Sample B                                    ______________________________________                                        ME #1                                                                         DI water              212.84                                                  Anionic Surfactant (23% active)                                                                     43.68                                                   Methyl Methacrylate   557.02                                                  Butyl Acrylate        73.43                                                   Styrene               55.42                                                   Methacrylic acid      6.93                                                    ME #2                                                                         DI water              212.84                                                  Anionic Surfactant (23% active)                                                                     43.68                                                   Butyl Acrylate        372.70                                                  Methyl Methacrylate   146.90                                                  Hydroxyethyl Methacrylate                                                                           138.60                                                  Methacrylic acid      34.60                                                   ______________________________________                                    

                  TABLE 2.3                                                       ______________________________________                                        Monomer Emulsions used in Comparative Sample C                                ______________________________________                                        ME #1                                                                         DI water              212.84                                                  Anionic Surfactant (23% active)                                                                     43.68                                                   Methyl Methacrylate   557.02                                                  Butyl Acrylate        73.43                                                   Styrene               55.42                                                   Methacrylic acid      6.93                                                    ME #2                                                                         DI water              212.84                                                  Anionic Surfactant (23% active)                                                                     43.68                                                   Butyl Acrylate        372.70                                                  Methyl Methacrylate   146.90                                                  Hydroxyethyl Methacrylate                                                                           69.30                                                   Acetoacetoxy ethyl Methacrylate                                                                     69.30                                                   Methacrylic acid      34.63                                                   ______________________________________                                    

                  TABLE 2.4                                                       ______________________________________                                        Monomer Emulsions used in Sample 3                                            ______________________________________                                        ME #1                                                                         DI water              212.80                                                  Anionic Surfactant (23% active)                                                                     43.60                                                   Methyl Methacrylate   335.34                                                  Acrylonitrile         138.56                                                  Butyl Acrylate        135.80                                                  Styrene               69.29                                                   Methacrylic Acid      6.93                                                    Allyl Methacrylate    6.93                                                    ME #2                                                                         DI water              212.80                                                  Anionic Surfactant (23% active)                                                                     43.60                                                   Butyl Acrylate        360.29                                                  Methyl Methacrylate   159.36                                                  Acetoacetoxy ethyl Methacrylate                                                                     138.57                                                  Methacrylic acid      34.64                                                   ______________________________________                                    

                  TABLE 2.5                                                       ______________________________________                                        Monomer Emulsions used in Sample 4                                            ______________________________________                                        ME #1                                                                         DI water              212.80                                                  Anionic Surfactant    43.68                                                   Methyl Methacrylate   491.93                                                  Butyl Acrylate        90.07                                                   Styrene               69.29                                                   Methacrylic acid      34.64                                                   Allyl Methacrylate    6.93                                                    ME #2                                                                         DI water              212.80                                                  Anionic Surfactant    43.68                                                   Butyl Acrylate        415.72                                                  Acetoacetoxy ethyl Methacrylate                                                                     138.57                                                  Acrylonitrile         69.29                                                   Methacrylic acid      34.64                                                   Styrene               34.64                                                   ______________________________________                                    

EXAMPLE 3 Preparation and Evaluation of waterborne coating compositions

Preparation of Composition land Comparative Compositions a-e. Waterbornecompositions were prepared by adding the ingredients with stirring, inthe order given in Table 3.1.

                                      TABLE 3.1                                   __________________________________________________________________________    Waterborne Composition i and Comparative Compositions a-e.                    Waterborne     Comp.                                                                             Comp.                                                                             Comp.                                                                              Comp.                                                                             Comp.                                         Composition                                                                              i   a   b   c    d   e                                             __________________________________________________________________________    Sample 2   700 700 --  --   --  --                                            Comp. Sample B                                                                           --  --  700 700  --  --                                            Comp. Sample C                                                                           --  --  --  --   700 700                                           EB         7.9 7.9 7.9 7.9  7.9 7.9                                           TEGOGLIDE 410                                                                            1.05                                                                              1.05                                                                              1.05                                                                              1.05 1.05                                                                              1.05                                          (50% in EB)                                                                   ACRYSOL RM-825                                                                           5.2 5.2 5.2 5.2  5.2 5.2                                           (5% solids in water)                                                          BAYHYDUR XP-                                                                             13.1                                                                              0   13.1                                                                              0    13.1                                                                              0                                             7063                                                                          Water (to 24 +/- 2                                                                       0   0   60.7                                                                              92.8 25.0                                                                              17.9                                          sec. #2 Zahn)                                                                 __________________________________________________________________________     Notes to Table 3.1:                                                           1) EB = ethylene glycol monoethyl ether                                       2) TEGOGLIDE is a trademark of Tegochemie Service USA; TEGOGLIDE is a sli     aid.                                                                          3) ACRYSOL is a trademark of Rohm and Haas Co. ; Acrysol RM825 is a           rheology modifier.                                                            4) BAYHYDUR is a trademark of Miles Inc.; BAYHYDUR XP7063 is a                waterdispersible polyisocyanate bearing at least two isocyanate groups.  

Waterborne composition land Comparative Compositions a-e, at 2-4 hoursold, were applied to maple veneer wood panels using a conventionalair-spray gun. The maple panels had two coats, 1.0 mil dry filmthickness each, with light sanding between coats. After 20 minutesflash-off period, panels were force-dried for 10 minutes at 140 F. aftereach coat, and cured for 5 days at 33° C. prior to testing. Test resultsare presented in Table 3.2.

                  TABLE 3.2                                                       ______________________________________                                        Evaluation of cured Waterborne compositions i-iii and                         Comparative Compositions a-c                                                  Waterborne       Comp.   Comp. Comp. Comp. Comp.                              Composition                                                                              i     a       b     c     d     e                                  ______________________________________                                        16 hour spot tests                                                            on maple veneer,                                                              after recovery                                                                (0-10 scale, 10                                                               best):                                                                        7% ammonia 5     1       1     0     3     1                                  1% DREFT   8     6       6     5     6     5                                  detergent solution                                                            ______________________________________                                    

The chemical and stain resistance of cured fillm of waterbornecomposition i of this invention is superior to that of ComparativeCompositions a-e.

EXAMPLE 4 Preparation and Evaluation of waterborne coating compositions

Preparation of Compositions ii-iv and Comparative Compositions f-h.Waterborne compositions were prepared by adding the ingredients withstirring, in the order given in Table 4.1.

                                      TABLE 4.1                                   __________________________________________________________________________    Waterborne Compositions ii-iv and Comparative Compositions f-h.               Waterborne Comp.   Comp.        Comp.                                         Composition                                                                              f   ii  g   iii  iv  h                                             __________________________________________________________________________    Sample 3   181.63                                                                            181.63                                                                            --  --   --  --                                            Sample 4   --  --  184.94                                                                            184.94                                                                             --  --                                            Sample 1   --  --  --  --   200.00                                                                            --                                            Comp. Sample A                                                                           --  --  --  --   --  200.0                                         DPM        2.8 2.8 2.8 2.8  --  --                                            TEGOGLIDE 410                                                                            0.42                                                                              0.42                                                                              0.42                                                                              0.42 0.4 0.4                                           (50% in EB)                                                                   ACRYSOL RM-825                                                                           25.2                                                                              23.03                                                                             29.03                                                                             22.62                                                                              22.0                                                                              18.0                                          (1% solids in water)                                                          Water      6.00                                                                              9.07                                                                              --  5.70 48.5                                                                              39.5                                          BAYHYDUR XP-                                                                             --  6.00                                                                              --  6.00 --  --                                            7063                                                                          BAYHYDROL XP-                                                                            --  --  --  --   7.70                                                                              7.70                                          7043                                                                          __________________________________________________________________________     Notes to Table 4.1:                                                           1) DPM = dipropylene glycol monomethyl ether                                  2) EB = ethylene glycol monoethyl ether                                       3) TEGOGLIDE is a trademark of Tegochemie Service USA; TEGOGLIDE is a sli     aid.                                                                           4) ACRYSOL is a trademark of Rohm and Haas Co. ; Acrysol RM825 is a          rheology modifier.                                                            5) BAYHYDUR is a trademark of Miles Inc.: BAYHYDUR XP7063 is a                waterdispersible polyisocyanate bearing at least two isocyanate groups.       6) BAYHYDROL is a trademark of Miles Inc.: BAYHYDOL XP7043 is a               waterdispersible polyisocyanate bearing at least two isocyanate groups.  

Waterborne compositions ii-iv and Comparative Compositions f-h, at 1-4hours old, were applied to maple veneer wood panels using a conventionalair-spray gun. The maple panels had two coats applied, each coat was1.0-1.2 mils dry film thickness, with light sanding in between coats.After a brief flash-off period, panels were force-dried and curedovernight at 120° F prior to testing. Test results are presented inTable 4.2.

                  TABLE 4.2                                                       ______________________________________                                        Evaluation of cured Waterborne compositions ii-iv and                         Comparative Compositions f-h                                                  Waterborne  Comp.          Comp.          Comp.                               Composition f       ii     g     iii  iv  h                                   ______________________________________                                        16 hour spot tests                                                            on maple veneer,                                                              after recovery                                                                (0-10 scale, 10                                                               best):                                                                        7% ammonia  1       5      2     2    5   7                                   1% DREFT    5       9      5     8    9   8                                   detergent solution                                                            10% sodium  8       8      3     9    8   7                                   carbonate                                                                     409 household                                                                             2       8      3     3    8   4                                   cleaner                                                                       50% Ethanol 6       8      6     8    6   3                                   1 hour spot tests on                                                          maple veneer, after                                                           recovery                                                                      (0-10 scale, 10                                                               best):                                                                        Butyl acetate                                                                             3       4      4     5    4   3                                   70% isopropanol                                                                           2       5      3     8    5   4                                   ______________________________________                                    

The chemical and stain resistance of cured fillms of waterbornecomposition ii of this invention is superior to that of ComparativeComposition f; as is waterborne composition iii of this invention issuperior to that of Comparative Composition g; and as is waterbornecomposition iv of this invention is superior to that of ComparativeComposition h.

EXAMPLE 5 Preparation and Evaluation of waterborne coating compositions

Preparation of Compositions v-vi and Comparative Compositions j-l.Waterborne compositions were prepared by adding the ingredients withstirring, in the order given in Table 5.1. Comparative Sample D was anacrylic latex polymer free from hydroxyl, amino, or active methylenegroups.

                  TABLE 5.1                                                       ______________________________________                                        Waterborne Compositions v-vi and Comparative                                  Compositions j-l.                                                             Waterborne   Comp.   Comp.   Comp.                                            composition  j       k       l     v     vi                                   ______________________________________                                        Comp. Sample D                                                                             180.0   --      159.7 --    --                                   Sample 2     --      180.0   --    162.6 162.6                                EB           --      --      2.5   --    --                                   EB:DEB 3:1 premix                                                                          6.9     6.9     --    --    --                                   TEGOGLIDE 410                                                                              0.4     0.4     0.4   0.5   0.4                                  (50% in EB)                                                                   ACRYSOL RM-825                                                                             2.7     2.9     1.9   2.4   1.4                                  (5% solids in water)                                                          Water        25.2    34      26.6  33.2  23.9                                 BYK 346      0.2     0.3     0.2   0.4   0.4                                  DESMODUR VP LS                                                                             --      --      11.2  11.2  --                                   2032 (Bayer)                                                                  BASONAT P LR --      --      --    --    11.2                                 8878 (BASF)                                                                   ______________________________________                                         Notes to Table 5.1:                                                           1) DEB = diethylene glycol monobutyl ether                                    2) EB = ethylene glycol monoethyl ether                                       3) TEGOGLIDE is a trademark of Tegochemie Service USA; TEGOGLIDE is a sli     aid.                                                                          4) ACRYSOL is a trademark of Rohm and Haas Co. ; Acrysof RM825 is a           rheology modifier.                                                            5) BYK 346 is a trademark of BykMallinkrodt Co.                               6) DESMODUR is a trademark of BAYER AG: DESMODUR VP LS 2032 is a              waterdispersible polyisocyanate bearing at least two isocyanate groups.       5) BASONAT is a trademark of BASF AG: BASONAT P LR 8878 is a                  waterdispersible polyisocyanate bearing at least two isocyanate groups.  

Waterborne Compositions v-vi and Comparative Compositions j-l, at 2-4hours old, were applied to maple veneer, NORYL 844 (NORYL is a trademarkof General Electric Corp.; polyphenylene oxide/polystyrene plastic), andprimed polypropylene panels using a compressed air spray gun. Plasticpanels had one coat at 1.0 mils dry film thickness/coat. Maple panelshad two coats, 1.0 mils film thickness, with light sanding in betweencoats. Panels were dried under ambient conditions and aged for one weekprior to testing. Test results are presented in Table 5.2.

                                      TABLE 5.2                                   __________________________________________________________________________    Evaluation of cured Waterborne compositions v-vi and Comparative              Compositions j-l                                                              Waterborne                                                                    composition                                                                              Comp. j                                                                             Comp. k                                                                             Comp. l                                                                             v    vii                                         __________________________________________________________________________    16 hour spot tests on                                                         maple veneer, after                                                           recovery                                                                      (0-10 scale, 10 best):                                                        7% ammonia 2     1     4     7    6                                           409 household                                                                            1     1     2     10   9                                           cleaner                                                                       1% DREFT   5     3     9     9    9                                           detergent solution                                                            50% Ethanol                                                                              5     6     9     10   9                                           1 hour spot tests on                                                          maple veneer, after                                                           recovery                                                                      (0-10 scale, 10 best):                                                        Butyl acetate                                                                            1     3     4     8    8                                           70% isopropanol                                                                          6     3     6     6    6                                           MEK double rubs on                                                                       5     6     12    25   20                                          NORYL 844  (dissolved)                                                                         (dissolved)                                                                         (dissolved)                                                                         (cracks)                                                                           (cracks)                                                           (cracks)                                               __________________________________________________________________________     Notes to Table 5.2:                                                           1) DREFT is a trademark of Procter and Gamble Co.                             2) NORYL is a trademark of General Electric Corp.                        

The chemical and stain resistance of cured films of waterbornecompositions v-vi of this invention are superior to that of ComparativeCompositions j-l.

EXAMPLE 6 Preparation and Evaluation of waterborne maintenance coatingcompositions

Preparation of maintanance coating Composition vii and ComparativeCompositions m-o. Waterborne compositions were prepared with theingredients given in Table 6.1. Water 1, TAMOL 681M, Ammonia, TRITONCF-10, and TIONA RCL-628 were dispersed using a high speed Cowlesdissolver. The the other ingredients were added with stirring, in theorder given.

                  TABLE 6.1                                                       ______________________________________                                        Waterborne Composition vii and Comparative                                    Compositions m-o.                                                             Waterborne    Comp.   Comp.     Comp.                                         composition   m       n         o     vii                                     ______________________________________                                        Comp. Sample A                                                                              --      182.0     163.3 --                                      Sample 1      181.01  --        --    162.24                                  water 1       11.24   11.24     11.24 11.24                                   TAMOL 681M    1.64    1.64      1.64  1.64                                    Ammonia (28%) 0.14    0.14      0.14  0.14                                    TRITON CF-10  0.19    0.19      0.19  0.19                                    TIONA RCL-628 39.79   39.79     39.79 39.79                                   water 2       9.44    7.73      19.38 21.02                                   ACRYSOL RM-825                                                                              0.88    0.92      0.90  0.75                                    BAYHYDROLXP-  --      --        6.90  6.84                                    7043 Miles)                                                                   ______________________________________                                         Notes to Table 6.1:                                                           1) TAMOL is a trademark of Rohm and Haas Co.; Tamol 681M is an anionic        pigment dispersant                                                            2) TRITON is a trademark of Union Carbide Co.; TRITON CF10 is a anionic       surfactant                                                                    3) TIONA is a trademark of SCM Chemicals; TIONA RCL628 is titanium dioxid     4) ACRYSOL is a trademark of Rohm and Haas Co. ; Acrysol RM825 is a           rheology modifier.                                                            5) BAYHYDROL is a trademark of Miles Co.: BAYHYDROL XP7043 is a               waterdispersible polyisocyanate bearing at least two isocyanate groups.  

Treated Aluminium panels were coated with an epoxy primer(Sherwin-Williams Co. Tile-Clad II) using a 10 mil drawdown blade whichgave a 2 mil dry film thickness. The samples were dried for one daybefore the topcoat was applied. Topcoat waterborne composition vii andComparative Compositions m-o were drawn down using a 10 mil blade whichgave a 2 mil dry film thickness; the coatings were cured for 5 days atambient conditions before testing. The spot tests were carried out byplacing a 1 inch by 1 inch square cheesecloth on the coating andsaturating the cheesecloth with the test liquid. Test results arepresented in Table 6.2.

                  TABLE 6.2                                                       ______________________________________                                        Evaluation of cured Waterborne compositions vii and                           Comparative Compositions m-o                                                  Waterborne     Comp.   Comp.     Comp.                                        composition    m       n         o     vii                                    ______________________________________                                        spot tests                                                                    (1-5 scale, 5 best):                                                          3.7% HCl; 30 min.                                                                            5       5         5     5                                      saturation                                                                    2% NAOH; 30 min.                                                                             5       4         4     4                                      saturation                                                                    xylene; 6 hrs. 1       1         1     5                                      saturation                                                                    butyl acetate; 6 hrs.                                                                        1       1         1     5                                      saturation                                                                    MEK, 6 hrs. saturation                                                                       1       1         1     5                                      MEK double rubs                                                                              59      53        83    >600                                   ______________________________________                                         Note to Table 6.2:                                                            1) MEK is methyl ethyl ketone                                            

The chemical resistance of the cured maintenance coating film ofwaterborne composition vii of this invention is superior to those ofComparative Compositions m-o.

What is claimed is:
 1. A method of improving the chemical resistance ofa coating comprising:(a) forming a waterborne coating composition byadmixing an aqueous dispersion of a polymer, said polymer beingsubstantially free from hydroxyl, primary amino, and secondary aminogroups and said polymer bearing at least two active methylene groups;and an aqueous dispersion of a polyisocyanate bearing at least twoisocyanate groups; (b) applying said coating composition to a substrate;and (c) curing said coating composition.
 2. The method of claim 1wherein said active methylene groups are selected from the groupconsisting of acetoacetates, acetoacetamides, cyanoacetates, andcyanoamides.
 3. The method of claim 1 wherein said polymer is anaddition polymer formed by an emulsion polymerization of at least twoethylenically unsaturated monomers, said monomers comprising from about5% to about 25% by weight, based on the weight of said addition polymer,acetoacetoxyethyl methacrylate.
 4. The method of claim 3 wherein saidaddition polymer has a glass transition temperature from about -30° C.to about 45° C.
 5. The method of claim 1 wherein said polyisocyanatecomprises isocyanate groups selected from the group consisting ofaliphatically bound isocyanate groups, cycioaliphatically boundisocyanate groups, and mixtures thereof.
 6. The composition of claim 1wherein said polyisocyanate comprises isocyanurate groups, saidpolyisocyanate having been formed from 1,6-hexamethylene diisocyanate.